That the produce of land increases, _cæteris paribus_, in a diminishing ratio to the increase in the labor employed, is, as we have said (allowing for occasional and temporary exceptions), the universal law of agricultural industry. This principle, however, has been denied. So much so, indeed, that (it is affirmed) the worst land now in cultivation produces as much food per acre, and even as much to a given amount of labor, as our ancestors contrived to extract from the richest soils in England. The law of diminishing returns is the physical fact upon which the economic doctrine of rent is based, and requires careful attention. Carey asserts, instead, that there is a law of increasing productiveness, since, as men grow in numbers and intelligence, there arises an ability to get more from the soil.(132) Some objectors even deny that different grades of land are cultivated, and that there is no need of taking inferior soils into cultivation. If this were true, why would not one half an acre of land be as good as a whole State? Johnston(133) says: “In a country and among poor settlers ... poor land is a relative term. Land is called poor which is not suitable to a poor man, which on mere clearing and burning will not yield good first crops. Thus that which is poor land for a poor man may prove rich land to a rich man.”(134) Moreover, as is constantly the case in our country, it often happens that a railway may bring new lands into competition with old lands in a given market; of which the most conspicuous example is the competition of Western grain-fields with the Eastern farms. In these older districts, before the competition came, there was a given series of grades in the cultivated land; after the railway was built there was a disarrangement of the old series, some going out of cultivation, some remaining, and some of the new lands entering the list. The result is a new series of grades better suited to satisfy the wants of men.